1. Field of the Invention:
This invention relates to an apparatus and method for aligning solid components having rigid projections in preparation for pickup of the solid component by a robotic mechanism. More particularly, it relates to an apparatus and method that maintains an alignment with solid components having rigid projections depending therefrom, in three dimensional space, while independently grasping external surfaces of the solid component for pickup and placement at a remote location.
2. Discussion of the Prior Art:
The present invention pertains to the automated robotic placement of solid components at an accurately determined location. Since the placement accuracy of many robotic insertion heads is directly related to the accuracy of positioning the robotic head during pickup of the solid component, convenient, accurate alignment techniques, compatible with an automated pickup process, are necessary.
One example of a solid component being robotically placed, is an electrical connector of the type having a dielectric body, with one or more arrays of outwardly extending metallic terminal pins mounted therein. For a totally automated placement of such connectors, an accumulation of placement inaccuracies must be considered, and the sum total of all such inaccuracies must be carefully controlled. For example, the terminals of such connectors are typically inserted in mounting holes drilled in a printed circuit board. In a fully automated precess, a robotic pickup and insertion head would acquire a connector from a remote source such as a tray or the like, would move to a position on the printed circuit board, and would lower a predetermined amount, thereby inserting the connector terminals in the mounting holes of the printed circuit board. However, with the increasing number of leads required in connectors, the closer spacing between leads and the closer spacing of components on the printed circuit board, it is becoming increasingly difficult to position each terminal of an array of a large number of closely spaced terminals in the array of mounting holes in the printed circuit board.
In addition to inaccuracies of positioning successive printed circuit boards relative to a robotic insertion head, the inaccuracies of robotic movement from origin to destination, and the inaccuracies of the location of mounting holes relative to printed circuit board positioning holes, there is an inaccuracy in the position of connector terminals relative to the housing edge surfaces which are typically engaged by a robotic gripper head. The aggregate effect of these inaccuracies renders it difficult to insert all the leads of a connector into all of the printed circuit board mounted holes simultaneously, without causing damage to the leads or to the mounting holes.
When loading connector terminals in a connector housing, it is possible to maintain their precise location with respect to each other with a fairly high degree of accuracy. Unfortunately, however, the position of the connector terminals with respect to external edge surfaces of the connector housing may vary significantly from connector to connector. In the past, attempts to automatically align the pins of the connector to the printed circuit board have used the external edges connector housing as the reference for alignment. Since the terminals have a potential error in placement with respect to the connector housing, they also have a potential error in placement with respect to the mounting holes. Hence, the common technique used in the prior art to align the terminals to the mounting holes is to place the connector on the printed circuit board so that terminals of the connector are approximately aligned with the mounting holes. Final alignment is accomplished by an additional automated process or manually, by an operator.
One example of an alignment apparatus and method for use with an automated assembly process, is described in U.S. Patent No. 4,479,298. The patent addresses the need of accurately positioning the various wafer-like stages of an integrated circuit (IC) package assembly. The technique used requires an alignment fixture, comprising a coarse alignment pedestal mounted on a fine alignment block, for receiving the IC package and aligning the leads thereof with respect to a two dimensional reference coordinate system. The leads of the package, however, are of a surface mount type, having solder pads extending parallel to the wafer-like body. The arrangement disclosed is for fixing the location of the leads, relative to the remainder of the IC package, and does not address the need for accurately positioning a component in three dimensional space in preparation for pickup by a robot arm or the like automated assembly technique.
United Kingdom patent application 2,131,331 describes a technique to aid in the robotic placement of a plurality of different shaped components on a printed wiring board. The technique uses a template designed for use with a particular printed wiring board, having accurately dimensioned openings for rceiving the plurality of electronic components. To aid in seating the components in the template and to aid introducing the leads thereof into the mounting holes of the printed wiring board, and template and board are vibrated. This technique is not concerned with the accurate pickup of a component with a robotic arm, since it compensates for any inaccuracies by using the template to guide the components after they are robotically placed at their final destination.
U.S. Pat. No. 4,459,743 describes a technique for the automatic mounting of chip components, stored in a parts hopper, for placement on a printed circuit board. The system uses a combination of X direction and Y direction shuttle mechanisms. The components are conveyed downwardly along a sliding track, with the outermost projecting surface thereof coming to rest against a stopper member. Thereafter, the part is conveyed to the X-Y conveyance apparatus.
U.S. Pat. No. 4,470,182--Zemek et al, discloses an arrangement for centering electrical components that are mounted on a paper tape substrate. The arrangement displaces the components along their longitudinal centerlines, in a direction perpendicular to the axis of the paper tape substrate. The arrangement uses a pair of spaced apart arms which come together, to provide an automatic centering of the components, relative to the centerline of the arm mechanism.
It is therefore apparent that a need exists in the art for an apparatus and method to accurately align the terminals of an electrical connector to the mounting holes of a printed circuit board to which the connector is to be mounted. Such an apparatus and method, if compatible with automated robotic insertion techniques would not only lower the manufacturing costs but also would improve the quality of the electronic device produced.